Our goals in this research are to determine the role of maturational constraints and the effects of language competence in the ontogeny of the brain systems that mediate primary language acquisition in normal development. Our approach will be to assess changes in brain organization that occur as a function of chronological age and to contrast these with changes linked to specific language abilities when age is held constant. Thus, we will contrast functional cerebral specializations in infants and children who are in the middle, and at the upper and lower ends of the normal distribution for language comprehension and production. We will record event-related brain potentials (ERPs) from over several brain regions within and between the cerebral hemispheres in a series of studies designed to assess different aspects of sensory, language and non-language cognitive processing. The specific aims of the series of experiments include: 1. To determine (a) the developmental time course of mature patterns of cerebral specializations for language processing and their relation to the attainment of specific language milestones, (b) the limits of ERPs as an index of word comprehension in early lexical development, (c) the nature of cross-modal integration of semantically related information as the lexicon develops, (d) when the developing lexicon displays a semantic organization (i.e. priming) and whether this organization is predicted by levels of language abilities or chronological age. To assess the hypotheses that (a) different neural systems mediate semantic and syntactic processing of language from an early age, (b) the mature pattern of cerebral organization associated with aspects of semantic processing is evident at an earlier age than is that characteristic of grammatical processing, (c) different neural systems, mediate language and non-language cognitive processing at all ages and, levels of development, (d) the functional specializations of the right hemisphere for face recognition are preceded by and depend upon the development of left hemisphere specialization for language. (e) the differentiation of sensory systems occurs along a different (earlier) time course than the specialization of language systems.